3. Results and discussions
3.1. Structure of nanocomposites
Fig. 1 shows the XRD pattern of nanoclay and rubber–nanoclay
composites. Cloisite 15A shows the diffraction peak at 2u value of
3.38 (Fig. 1a) and corresponds to interlayer spacing of 26.75 A˚
(calculated as per Bragg’s diffraction equation 2d sin u = nl, where
d is the interlayer spacing of nanoclay, u = reflection angle,
n = order of reflection and it is 1 and l = wavelength of X-ray
used for diffraction experiment). At 3 wt.% nanoclay filled rubber,
the diffraction peak shifts to lower angle of 2.788 (Fig. 1b) and
corresponds to d spacing (interlayer distance) of 31.75 A˚ . This
result suggests that matrix rubber entered into the clay’s nanolayer
spacing and increased the d spacing of nanoclay by 5 A˚ . Such an
ordered arrangement of nanolayers of clay in matrix polymer is
called ‘intercalated’ nanocomposite structure. However, the XRD
pattern for nanoclay with 1 wt.% and 2 wt.% does not show any
diffraction peak. This suggests that the rubber has entered into the
clay’s interlayer spacing and separated the clay nanolayers to form
an intercalated structure in such a way that Bragg’s diffraction
peak cannot be obtained or clay nanolayers could have randomly
dispersed in polymer matrix. The random arrangement of
nanolayers of clay in polymer matrix is called an exfoliated
structure. Hence, XRD pattern confirms the formation of exfoliated
or well intercalated nanocomposites at lower clay content (1 and